ALLOCATE-FIXNUM-RANGE

(Allocate-fixnum-range fixnum-lo fixnum-hi) causes Gnu Common Lisp
(GCL) to create a persistent table for the integers between
fixnum-lo and fixnum-hi (both bounds inclusive). This table is
referenced first when any integer is boxed and the existing box in
the table is used if the integer is in bounds. This can speed up
GCL considerably by avoiding wasteful fixnum boxing. Here,
fixnum-lo and fixnum-hi should be fixnums, more specifically of
type (signed-byte 29), with fixnum-lo <= fixnum-hi.

When this function is executed in a Lisp implementation other than
GCL, it has no side effect. This function always returns nil.